Agglomerated products such as briquettes, pellets and blocks made from fine derivatives of oxides and metals of iron, limestone, dolomite, dunite, solid carbon etc. by iron bearing hydraulic mineral binder will find suitable application as a feed material in blast furnace for extraction of iron, in rotary and shaft kiln for reduction and oxidising roasting and sintering, in tunnel, chamber and moving grate type of furnaces for calcinations, roasting and sintering.
Agglomeration methods of briquetting and pelletisation are quite well-known for converting fines and powdery derivatives of ores, minerals, residue and solid wastes into lumpy sizes for various industrial use. This is a common practice in iron and steel industries for use of Fe-containing fine materials in the metallurgical furnaces. Many process developments have been made for production of briquettes and pellets from various metallurgical fines by hot and cold methods. Depending on the nature of fines, oil contamination, mineral association and Fe-structural phases, both hot and cold processes have been developed to make briquettes and pellets.
Japanese patent no 8135, 731 dated 08 Apr. 1981 (C1. C22 B1/14), by Jpn. Kokai Tokkyo Koho (Sumitomo Metal Ind. Ltd.) describes production of cold iron ore briquettes using cement (OPC) by hardening at 90° C. for 24 hours and drying at 90° C. temperature for 1 hour to get crushing strength in the order of 256 kg.
De Souza Neto et al., Brazilian patent Pedido PI 7705, 932 dated 03 Apr. 1979 (C1. C22 B1/242), describes briquetting of Fe-ore fines using binders like hydrated lime, molasses, bentonite, Na-silicate, cement (OPC/pozz.), Na2SO4, tar. dextrin or maniac flour.
Nippon Kokan K. K.et al.'s, Japanese Patent No. JP 60 33 319 (85 33 319) dated 20 Feb. 1985 (C1. C22 B1/14), describes use of 5 to 15% basic slag as binder in making briquettes of ferrous and non-ferrous ores by heat treatment at 5 to 200° C. temperature, and steam curing.
Nippon Kokan K. K. and Kokai Tokkyo Koho's Japanese Patent No. 80, 100, 940 dated Aug. 1, 1980 (C1. C22 B1/14) describes use of cement (OPC) as binder in briquetting iron ore by curing for 3 days at room temperature and then steam curing at 100° C. and then drying at 100 to 500° C. for development of strength.
Austin Lawrence J. and et al., German Patent No. 2,614,452 dated 13 Oct. 1977 (C1 C22 B1/244), describes briquetting of sponge Fe-dust with bituminous binder such as aq. emulsion of mineral oil.
Knill Kenneth G. et al., German Patent No. 2,605,215 dated 26 Aug. 1976 (C1. B22 F1/00), describes briquetting of steel shavings, turnings and scrap dust using fibrous material, high alumina cement, limestone as binder.
“Present state of sponge iron briquettes in consideration of the selection of the binder agent” by Maschinenfabrik, Koeppern GmbH and Co., K-G, Hattinger Fed. Rep. Ger., MPT Metall. Plant Technol., 1981, 5(2) illustrates the use of waterglass, molasses, spent sulphate lye, pitch and bitumen as binder for hot and cold briquetting of sponge iron fines.
Kudryavtsev, O. M. et al. (USSR) Intensif. Protesessov. Domennoi Plavki Osvoenie Pechei Bol'shogo Ob'ema, 1979 (5) 28-30 illustrates hot briquetting for metallised fines at 700 and 800° C. temperature.
Kiwaki Yoshihiro et al. (Onoda Cement Co. Ltd., Nippon Steel Corp.), Jpn. Kokai Tokkyo Koho, JP 60, 184, 642 (85, 184, 642) (C1. C22 B1/243), 20 Sep. 1985 patent describes use of cement (OPC) as a binder for briquetting of Fe-ore fines.
Similarly, the processes in production of Fe-pellets, Lotosh V. E. et al., USSR Patent No. 730, 844 (C1. C22 B1/243), 06 May 1980 describes use of cement (OPC), earth metals and chloride salts as a mechanical activator for production of cold bonded iron ore pellets.
Salykin A. A. et al., USSR Patent No. 648, 626 (C1. C22 B1/243), 25 Feb. 1979 describes use of binding agents like polymethacrylamide, soda, bentonite in cold pelletisation of iron ore materials.
Sasaba Minoru, Tetsu to Hogan, 1985, 71 (15), 1780-6 Japan illustrates use of specially developed binder from LD slag and alumina sludge mixtures by melting for making cold bonded Fe-ore pellets.
Furui Takeo et al. (Nippon Steel Corp.) Japan Kokai 7711103 (C1. C22B1/14), 27 Jan. 1977 patent discloses the use of cement clinker and limestone mixture as binder which is mixed with iron ore material by grinding for production of non-sintered pellets.
Munrio Neil et al. (British steel Corp.) Ger Offen. 2, 622, 348 (C1. C22 B1/14), 02 Dec. 1976 patent discloses use of bentonite and water as binder for making Fe-ore pellet by sintering on grate to obtain desired strength and properties for BF application.
Earlier inventions disclose the use of various types of organic and inorganic materials such as lime, molasses, cellulose, dextrin, resin, bentonite, plastic clay, limestone, dolomite, cements, slag, mineral oil, tar, phenol, earth metal silicate, chloride and sulphates as binders in briquetting and pelletisation of iron-containing ores and fines by hot and cold methods which involves curing at normal atmospheric condition, under steam pressure, under heat at 200 to 800° C. temperature for hardening to make suitable for B.F. use. Some of the processes also describes sintering of cold bonded briquettes and pellets at 1200° C. temperature for blast furnace use. Some of the process further describes use of oil contaminated iron-sludge by heating for de-oiling and hot briquetting.
The drawbacks of the earlier processes are the use of wide varieties of binding materials, steam curing, heat hardening, sintering and hot compaction under pressure in making briquettes and pellets which are energy intensive. Most of the organic and inorganic binders dissociate at low temperature (below 600° C.) and easily soluble in water for which the briquettes and pellets made out of these binders give unsatisfactory performance in respect to durability, resistance to moisture, volume stability and thermal stability. In addition, the use of sulphate, alkali, chloride, phosphate bearing binding materials results in poor sinterability and reducibility of briquettes and pellets. These types of binders also add deleterious impurities in the metallurgical process and create emission of hazardous and corrosive gases which cause destruction of furnace life and air pollution. Thus there exists a need to provide a process that overcomes the aforesaid limitations.